An exemplary light source device is a backlight device of a liquid crystal display unit. Such a light source device emits light from a main surface of a light guide plate on which light from a light source is incident. The light source may be a cold cathode fluorescent lamp (CCFL) which is a linear light source and a light emitting device (LED) which is a point light source.
With the above light source device, however, when, for example, plural linear light sources are arranged to provide a large-sized light source device or plural point light sources are arranged to provide even a small-sized light source device, a degree of non-uniformity in brightness tends to increase in a vicinity of a light incident portion of the light guide plate in which light from the plural light sources is introduced because of the existence of non-light emitting portions between the light sources. Under these circumstances, techniques of controlling an increase in the degree of non-uniformity in brightness have been developed and disclosed in, for example, PTLs 1 and 2.